Recently, because of the increase of interest in environments and energies, needs for industrial products relative to energy conservation are high, and as one of these, glass and a film which are effective in heat shielding of window glass of houses, automobiles or the like, that is, in reducing a heat load caused by sunlight are required. In order to reduce a heat load caused by sunlight, it is necessary to prevent the transmission of sunbeam in either the visible light region or the infrared region in the sunlight spectrum.
A glass frequently used as an ecoglass having a high heat insulating/heat shielding properties is a multi-layered glass referred to as a Low-E pair glass with a coating of a special metal film that shields a heat ray. The special metal film can be made by laminating plural layers, for example, by a vacuum film forming method. The coating of these special metal films, which is made by vacuum film forming, is remarkably excellent in reflection performance, but a vacuum process has low productivity and leads to high production cost. Furthermore, since the use of a metal film simultaneously results in the shielding of electromagnetic waves, there are problems in which electromagnetic interference is caused in the use of mobile phones or the like and ETC can not be used when the film is used for automobiles.
In contrast to this, a method of selectively reflecting infrared ray through the use of a cholesteric liquid crystal described in Patent Literature 1 is known, and since in the method described in Patent Literature 1 only infrared rays can reflected, the problem of the shielding of electromagnetic waves can be solved.
However, when trying to cut infrared rays over a broad zone only by a cholesteric liquid crystal, the number of layers to be laminated becomes large because the width of selective reflection wavelength by a cholesteric liquid crystal is narrow. In addition, in the case of cutting wavelengths on a long wavelength side (1200 to 2000 nm) by the selective reflection of a cholesteric liquid crystal, a large film thickness is needed, to thereby raise material cost in the actual circumstances. For example, in Patent Literature 1, 4 or more cholesteric reflecting layers and a layer containing a metal oxide that absorbs 1400 to 2500 nm are provided by application and 5-time applications were necessary at this point. Note that, in order to furthermore improve heat shielding performance in the configuration in Patent Literature 1, a reflecting layer that furthermore reflects wavelengths of less than 1400 nm is necessary and, in that case, 6 or more applications become necessary.
Furthermore, in Patent Literature 2, an infrared absorbing material formed by combining a cholesteric liquid crystal layer and a tungsten oxide compound is described.